In Ader's experiment immune responsiveness was conditioned just like the behavior salivation in Pavlov's experiment. Ader used a drug called Cyclophosphamide, which irritates the stomach, as the biologically-salient stimulus, and paired it with flavored water as the neutral stimulus. But to Ader's surprise, many of the experimental rats died--not being an immunologist, Ader failed to realize that Cyclophosphamide was an Immuno-suppressor, and a powerful one at that.
Ader then gave the surviving rats an "antigenic challenge" by injecting them with sheep red blood cells (erythrocytes), that caused the rats to make antibodies against the sheep's "foreign cells." Upon measuring the antibody response Ader found that rats fed the Cyclophosphamide produced less antibodies to sheep erythrocytes. The rats given sheep erythrocytes and flavored water--without Cyclophosphamide--also produced less antibodies. The once-neutral flavored water by itself suppressed the immune system because of its past association with the Cyclophosphamide--just like Pavlov's dogs did when they salivated to the bell. It seemed obvious to Ader that something in the rats' brain caused this response...it was learned and remembered.
These accounts are intentionally overly simplified for the purposes of this brief article. For example, I left out the discussion of various control groups and other details. But, the main findings have been replicated in this and other paradigms over and over since the 1970's and, as a result of Ader's and other prototypical studies, Psycho-Immunology as a distinct field of medical science, is on the map, so to speak.
For those of you who have taken Introductory Psychology, you may recognize the form of learning as "Classical" or "Pavlovian" conditioning. In this case a neutral stimulus (the flavor) takes on the power of a biologically-salient stimulus (the radiation) as a result of the paired association of the two stimuli.
And those of you familiar with the more modern advances in psychology may see that it's only short epistemological hop from the Classical Conditioning paradigm to the more advanced, and potentially useful, "Instrumental Training" to make Psycho-Immunology a therapeutic tool.
Biofeedback, a procedure wherein the patient (or trainee) is given a perceptible external signal that corresponds with an internal (normally imperceptible) event and then is trained to modify the external stimulus and, thereby, modifying the internal event. The simplest to demonstrate is heart rate, for just one of many examples of internal events subject to modification via biofeedback training.
Imagine sitting, with electrodes attached to your fingers, in front of a computer screen with a moving, squiggly line that goes up when your heart accelerates and goes down when your heart slows. There could even be a pre-determined (and adjustable) threshold set by you or the trainer, one that sounds a faintly audible tone when your heart rate descends below, say 70 beats per minute. The trainer tells you, "Your job is to make the tone sound for as long as you can."
